 /*******************************************************************************
  * Copyright (c) 2003, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal;

 import org.eclipse.ui.IPerspectiveDescriptor;
 import org.eclipse.ui.IPerspectiveListener;
 import org.eclipse.ui.IPluginContribution;
 import org.eclipse.ui.IWorkbenchPage;
 import org.eclipse.ui.PartInitException;
 import org.eclipse.ui.PlatformUI;
 import org.eclipse.ui.activities.IIdentifier;
 import org.eclipse.ui.activities.IIdentifierListener;
 import org.eclipse.ui.activities.IWorkbenchActivitySupport;
 import org.eclipse.ui.activities.IdentifierEvent;
 import org.eclipse.ui.activities.WorkbenchActivityHelper;
 import org.eclipse.ui.views.IViewDescriptor;

 /**
  * Helper methods that the internal layout classes (<code>PageLayout</code> and
  * <code>FolderLayout</code>) utilize for activities support and view creation.
  *
  * @since 3.0
  */
 class LayoutHelper {

     /**
      * Not intended to be instantiated.
      */
     private LayoutHelper() {
         //no-op
 }

     /**
      * Creates a series of listeners that will activate the provided view on the
      * provided page layout when <code>IIdenfier</code> enablement changes. The
      * rules for this activation are as follows: <p>
      * <ul>
      * <li> if the identifier becomes enabled and the perspective of the page
      * layout is the currently active perspective in its window, then activate
      * the views immediately.
      * <li> if the identifier becomes enabled and the perspective of the page
      * layout is not the currently active perspecitve in its window, then add an
      * <code>IPerspectiveListener</code> to the window and activate the views
      * when the perspective becomes active.
      *
      * @param pageLayout <code>PageLayout</code>.
      * @param viewId the view id to activate upon <code>IIdentifier</code> enablement.
      */
     public static final void addViewActivator(PageLayout pageLayout,
             final String viewId) {
         if (viewId == null) {
             return;
         }

         ViewFactory viewFactory = pageLayout.getViewFactory();

         final IWorkbenchPage partPage = viewFactory.getWorkbenchPage();
         if (partPage == null) {
             return;
         }

         final IPerspectiveDescriptor partPerspective = pageLayout
                 .getDescriptor();

         IWorkbenchActivitySupport support = PlatformUI.getWorkbench()
                 .getActivitySupport();

         IViewDescriptor descriptor = viewFactory.getViewRegistry().find(viewId);
         if (!(descriptor instanceof IPluginContribution)) {
             return;
         }

         IIdentifier identifier = support.getActivityManager().getIdentifier(
                 WorkbenchActivityHelper
                         .createUnifiedId((IPluginContribution) descriptor));

         identifier.addIdentifierListener(new IIdentifierListener() {

             /* (non-Javadoc)
              * @see org.eclipse.ui.activities.IIdentifierListener#identifierChanged(org.eclipse.ui.activities.IdentifierEvent)
              */
             public void identifierChanged(IdentifierEvent identifierEvent) {
                 if (identifierEvent.hasEnabledChanged()) {
                     IIdentifier thisIdentifier = identifierEvent
                             .getIdentifier();
                     if (thisIdentifier.isEnabled()) {
                         // show view
 thisIdentifier.removeIdentifierListener(this);
                         IWorkbenchPage activePage = partPage
                                 .getWorkbenchWindow().getActivePage();
                         if (partPage == activePage
                                 && partPerspective == activePage
                                         .getPerspective()) {
                             // show immediately.
 try {
                                 partPage.showView(viewId);
                             } catch (PartInitException e) {
                                 WorkbenchPlugin.log(getClass(), "identifierChanged", e); //$NON-NLS-1$
 }
                         } else { // show when the perspective becomes active
 partPage.getWorkbenchWindow()
                                     .addPerspectiveListener(
                                             new IPerspectiveListener() {

                                                 /* (non-Javadoc)
                                                  * @see org.eclipse.ui.IPerspectiveListener#perspectiveActivated(org.eclipse.ui.IWorkbenchPage, org.eclipse.ui.IPerspectiveDescriptor)
                                                  */
                                                 public void perspectiveActivated(
                                                         IWorkbenchPage page,
                                                         IPerspectiveDescriptor newPerspective) {
                                                     if (partPerspective == newPerspective) {
                                                         partPage
                                                                 .getWorkbenchWindow()
                                                                 .removePerspectiveListener(
                                                                         this);
                                                         try {
                                                             page
                                                                     .showView(viewId);
                                                         } catch (PartInitException e) {
                                                             WorkbenchPlugin.log(getClass(), "perspectiveActivated", e); //$NON-NLS-1$
 }
                                                     }
                                                 }

                                                 /* (non-Javadoc)
                                                  * @see org.eclipse.ui.IPerspectiveListener#perspectiveChanged(org.eclipse.ui.IWorkbenchPage, org.eclipse.ui.IPerspectiveDescriptor, java.lang.String)
                                                  */
                                                 public void perspectiveChanged(
                                                         IWorkbenchPage page,
                                                         IPerspectiveDescriptor perspective,
                                                         String changeId) {
                                                     // no-op
 }
                                             });
                         }
                     }
                 }
             }
         });
     }

     /**
      * Create the view. If it's already been been created in the provided
      * factory, return the shared instance.
      *
      * @param factory the <code>ViewFactory</code> to use.
      * @param viewID the view id to use.
      * @return the new <code>ViewPane</code>.
      * @throws PartInitException thrown if there is a problem creating the view.
      */
     public static final ViewPane createView(ViewFactory factory, String viewId)
             throws PartInitException {
         WorkbenchPartReference ref = (WorkbenchPartReference) factory
                 .createView(ViewFactory.extractPrimaryId(viewId), ViewFactory
                         .extractSecondaryId(viewId));
         ViewPane newPart = (ViewPane) ref.getPane();
         return newPart;
     }

 }

